In-filled Columns Research Articles

Experimental studies on the effect of nano silica modified novel concrete CFST columns

Under axial compression, the present article analyses and compares the behaviour of Plain Concrete filled and Nano Silica modified concrete filled with light gauge steel rectangular columns. In 18 work samples, plain and nano silica-modified concrete was tested on light gauge steel sections. Investigations were conducted into several essential variables, including the geometry of the cross-section, the tubular thickness of light gauge steel, the depth-to-thickness ratio, and the type of concrete infill used. From the experimental results, effects of flat width-to-thickness ratio (w/t), axial load-end shortening, axial load-deflection, axial load-strain characteristics, and failure modes have been studied under the linear stage. To evaluate their confinement effects, this study compared plain and silica-modified nano concrete tube columns with light gauge steel hollow hollow hollow columns. The experimental results are compared using BS5400, EC4, and ACI codes to determine the ultimate sectional capacity. Test outcomes showed that tested nano-silica modified concrete filled steel tubular (CFST) columns exhibited higher strength and outstanding ductility than the plain CFST and hollow light gauge steel columns. The nano silica-modified concrete in-filled columns showed a good yield plateau under the non-linear stage compared with the other columns.

Uniaxial compressive behaviour of a FRP standing support made of mine wastes

Twenty-seven specimens were tested to investigate the uniaxial compression behaviour of an innovative standing support for underground space applications. The innovative standing support consisted of an external fibre reinforced polymer (FRP) jacket and the infill column made of cementitious grout, tailings and coal wash rejects. Effects of the FRP layers number and water to the cementitious grout (w/g) ratio were evaluated. Test results indicated that lower w/g ratios produced stronger infill columns. With FRP confinement, the standing support demonstrated strain-hardening loading characteristics with a significant improvement in both strength and ductility. The highest strength and strain of the specimens achieved was 58.4 MPa and 11.8% respectively. Compared with the unconfined specimens, the confinement with four FRP layers increased the specimen strength and associated strain up to 3.6 and 27.0 times respectively. A correlation between the compressive strength of the infill material and the ultrasonic pulse velocity was also investigated. Furthermore, a simple design-oriented model was proposed to predict the peak strength and the corresponding strain of the innovative standing support.

Experimental Investigation on the Axial Compressive Behaviour of Cold-Formed Steel-Concrete Composite Columns Infilled with Various Types of Fibre-Reinforced Concrete

The exceptional structural strength and low cost of steel-concrete composite columns make them a popular choice for civil engineering structures. Numerous forms of composite columns, including steel tubes filled with concrete, have been produced recently in response to various construction situations. Cold-formed steel tubular columns with concrete filling have higher strength and ductility due to their capacity to withstand inner buckling and postpone outward buckling. The objective of this research is to determine the ductile and strength performance of composite columns containing various forms of fibre-reinforced concrete when subjected to axial compression. Several different kinds of fibre-reinforced concrete (FRC) are employed as additives in hollow steel columns, including steel FRC, carbon FRC, glass FRC, coir FRC, jute FRC, and sisal FRC. Axial compression tests were performed on 24 columns, including three hollow steel columns and 21 composite columns. Three distinct slenderness ratios were developed and used. Axial bearing capacity, compressive stress-strain curves, ductility, peak strain, axial shortening, and toughness were among the topics covered by the axial compression test. Experimental findings demonstrated that all conventional composite columns experienced failure through overall buckling, Local buckling and crushing of concrete infill, which was transformed into more ductile failure using fibre-reinforced concrete infills. The test results revealed that fibre-reinforced concrete-infilled steel columns outperformed conventional composite columns in terms of strength, ductility, and energy absorption capacity. The percentage increase in load-carrying capacity was observed as 203.88%, 193.48% and 190.03% when compared to hollow cold-formed steel tubular columns in medium, short and stub columns, respectively. Under assessment of stub, short, and medium columns, the load-strain plots demonstrated that the steel fibre-reinforced concrete in-filled columns performed well in terms of ductility. Localized buckling and crushing of the concrete infill caused the composite columns with low slenderness ratios to fail. In contrast, concrete-filled steel tube columns with higher slenderness ratios showed column failure through the overall buckling of the composite column.

State of Art—Light Gauge Steel Hollow and in-Filled Columns and Beams under Elevated Temperature

State of Art—Light Gauge Steel Hollow and in-Filled Columns and Beams under Elevated Temperature

Lateral Impact Response of Rubberized-Fibrous Concrete-Filled Steel Tubular Columns: Experiment and Numerical Study

This paper presents an experimental and numerical study on the lateral impact behavior of rubberized-fibrous concrete-filled steel tubular (CFST) columns. Four types of concrete were utilized in the experimental program in the infilled columns: normal concrete (NC), rubberized concrete (RuC), steel fiber concrete (SFC), and hybrid RuC-SFC. Twelve specimens were tested using drop-weight impact with fixed-sliding boundary conditions. Three different transverse impact energies were produced by applying two masses of the hammers dropped from two different heights. A high-speed camera was implemented to measure the mid-span deflection against time. A 3-D finite element model was presented and verified against the tested specimens and some other experimental work from the literature. Load-displacement curves, the impact force time history, impact energy absorption, and failure modes of the CFST columns under the lateral impact were fully analyzed. The present results showed that at, certain impact energies, the steel tubular suffered only from the plastic deformation, beyond which it started cracking depending on the type of filled concrete. The steel tubular filled with hybrid RuC-SFC showed the highest resistance to crack formation, followed by that filled with SFC, while those filled with NC showed the lowest resistance to crack formation. There is an agreement between the numerical and the experimental results.

In-plane cyclic testing of full-scale reinforced concrete frames with innovative isolated infill walls strengthened by highly ductile concrete

Conventional infilled frames exhibit weak seismic performance in high-intensity zones owing to the strong infill-frame interaction and vulnerability of the infill masonry. In this study, an innovative infill frame system with isolated infill walls retrofitted with highly ductile concrete (HDC) layers is proposed with the aim of minimizing the infill–column interaction and improving the lateral strength and deformation of masonry-infilled frames. Four full-scale specimens, including one bare frame, one conventional infilled frame, one conventional infilled frame retrofitted with HDC layers, and one isolated infilled frame retrofitted with an HDC layer, were tested under in-plane cyclic loading. The results indicated that the proposed isolated infill solution could effectively minimize the interaction between the isolated infill and columns. The observed damage on the isolated infill wall was minimal, whereas the damage to the columns was nearly identical to that of the bare frame. The isolated infill frame exhibited a higher lateral strength, deformation, and energy dissipation than the conventional infilled frame. Additionally, the proposed analytical model is highly consistent with the experimental results and can be used in design-oriented equations for innovative isolated infill frames.

An analytical study on nano-alumina modified concrete in-filled lightgauge steel fluted columns

Cold-formed steel sections are widely practiced cutting-edge of steel sections. A wide range of advantages prevails over the functioning of structural elements while cold-formed steel is been used along with the concrete in combination. Cold-formed steel in-filled columns filled with concrete have gained significance in the construction industry in recent times. Columns are built to withstand most of the axial load by the use of a thin-walled cold-formed steel tube by encasing the concrete. Far-reaching research regarding the behaviour, stress and strain characteristics of the columns using Cold-formed steel in-filled columns and the columns are stiffened using flutes which are provided along the length of the column as an integral part of the section of the column. The so-provided flutes will be triangular and rectangular in shape across the cross-section of columns. In this study, the behaviour of eighteen specimens with various types of flutes and thicknesses was examined. Analytical work was done using software for Finite Element Analysis. In this investigation, three cases with three, four, and five flutes each with a steel sheet thickness of one millimetre were taken into consideration. By the analytical investigation, the behavioural patterns of Cold-formed steel in-filled columns with flutes were carried out. From the analytical investigation implies that the load-bearing capacity of columns and the flute shape are directly related to the number of flutes in columns has an influential effect on resistance to higher loads.

WITHDRAWN: Analytical study on hollow and concrete in-filled columns with triangular and rectangular flutes under axial load

Abstract The ubiquitous stone column used in building construction in the ancient world was often fluted, it had parallel vertical grooves or channels cut into its surface. In this research, forty-two columns with different types of flutes and thickness were tested and their behaviour was studied. A Finite Element Analysis (FEA) model was developed to perform analysis of fluted columns subjected to compression. The cases with a different number of flutes such as 3, 4, and 5 respectively and with varying thickness of steel sheets 0.6 mm, 0.8 mm, 1 mm 1.2 mm, 1.4 mm, 1.6 mm, and 1.8 mm have been considered in this study. From the analytical investigation results it is understood that the increased number of flutes in columns directly effects on the load-carrying capacity of columns with five numbers of flutes having the highest load-carrying capacity, the lowest stress levels and less deflection relative to columns containing lesser number of flutes. The application of various thicknesses of column often has a strong impact on the ability to bear the load. The column with D/t of 88.88 exhibits greater load capacity, stress reduction, and lower deformation values compared to rest of column with different thickness.

Behaviour of Cold Formed Columns under Axial Loading with Quartz and Silica In-Filled Concrete

The experimental investigation was carried to study the investigate the behaviour of hollow, Plain Cement Concrete (PCC) and Silica; Quartz replaced concrete in-filled medium light gauge columns subjected to axial loads. The Cold formed sheets were welded continuously welded at the middle along its length. The basic study for the infill materials were carried out initially. For PCC in-fill M40 grade concrete were chosen. A total of 04 columns of 1.50m length were tested, without in fill, with plain concrete in-fill and with Quartz and Silica in-fill having a cross section of 100 x 50x 2mm. All the specimens were tested to failure. Ultimate load, Load – Axial shortening and Load-Strain for all the specimens tested were plotted. With the comparison of hollow columns the Quartz concrete in-filled columns take around 50% more ultimate loads when loaded axially. The in-filled column with Quartz withstands the maximum load; this is due to the fineness modulus property of the material. The Euro Code 4 predicted the ultimate loads closer to that of the experimental loads. Thus Quartz Sand can be used as an alternate filler material.

Seismic fragility of lightly reinforced concrete frames with masonry infills

SummarySeismic fragility of lightly reinforced concrete frames with masonry infills is assessed through numerical simulations considering uncertainty in ground motion and building materials. To achieve this aim, a numerical model of the components is developed, a rational approach to proportion and locate individual struts in the equivalent three‐strut model is proposed, and an explicit nonlinear column shear response model accounting for the infill–column interaction and soft‐story mechanism is employed. The proposed numerical model is used to (1) generate probabilistic seismic demand models accounting for a wide range of ground motion intensities with different frequency content and (2) determine limit state models obtained from nonlinear pushover analysis and incremental dynamic analysis. Using the demand and limit state model, fragility curves for the masonry‐infilled frames are developed to investigate the impact of various infill properties on the frame vulnerability. It is observed that the beneficial effect of the masonry infill diminishes at more severe limit states because of the interaction with the boundary frame. In some cases, this effect almost vanishes or switches to an adverse effect beyond a threshold of ground motion intensities. Copyright © 2015 John Wiley & Sons, Ltd.

Quality control of double fluid jet grouting below groundwater table: Case history

A jet grout block created by overlapping columns aimed to convert the saturated silty sand soils into a safe space for breaking down four underground parking uplift piles along the tunnel alignment. Since the grouting platform was located on the mat foundation in the basement of underground parking and was under the groundwater table, a series of dewatering wells were installed before the 177 columns were constructed to prevent intrusion of the groundwater flowing upward from sandy soil to basement through grouting hole during wash boring and grouting stages from happening. Several quality control measures were undertaken prior to quality assurance testing. Two measurements of spoil return and spoil flow rate for each column were implemented. From a back analysis from the mean values of spoil density and spoil flow rate, the column diameter was estimated at around 1.56m, slightly smaller than the design diameter by 2.5%. In addition, a control chart with upper and lower control limits, established from a large dataset of flow rate of spoil return, was a means to recognize the likelihood of sand boiling and to serve as an early warning indicator of abnormal conditions for the jet grouting works below the groundwater table. As the mean spoil density of the infill column was larger than perimeter column, an optimal grouting sequence for clusters was suggested in this paper. The jet grout block exposed during the breakdown process of the piles showed safe working conditions as required and a shield machine then passed through as planned.

Behaviour of concrete-filled steel columns subjected to lateral cyclic loading

This paper reports the findings of an experimental study that was undertaken to investigate the cumulative damage of in-filled steel columns subjected to quasi-static loading. The parameters studied are, the diameter-to-thickness ratio of the steel tube and two types of in-fills namely Plain cement concrete and Steel fiber reinforced concrete. This paper summarizes the results of phase I testing that consisted of benchmark tests to establish the hysteresis behaviour under variable amplitude cyclic loading and phase II testing that consisted of constant amplitude cyclic loading that focused on the effects of amplitude and number of cycles on damage accumulation of in-filled columns. Findings of these studies highlight the significant increase in ductility and energy absorption capacity and decrease in the damage index of Steel fiber reinforced concrete-filled steel columns compared to plain cement concrete-filled columns. A simplified equation for cumulative damage has been proposed to predict the damage index of in-filled columns. This index can be used as a measure for predicting the safety of new and existing in-filled columns against earthquake.

Responses of Concrete-Filled Cold-Formed Square Hollow and Double-C Steel Stub Columns under Cyclic and Repeated Loadings

This paper presents an experimental study on the response of 18 concrete-filled cold-formed square hollow and double-C steel stub columns under cyclic and repeated loading. The test parameters were (1) infilled materials, i.e. No fill, concrete infilled and mortar infilled columns (2) cross sectional shape and dimension. The effect of lips in double-c section as inside stiffeners is presented. The cyclic tested results indicate the infilled columns possess higher bearing capacity, especially infilled materials with higher strength and non-compact section columns. However, there is no different in ultimate tensile. Moreover, the infilled columns showed larger area under post-yield hysteretic loops leading to better seismic performance. Failure of columns was modified in which the failure mode was shifted from the in-outward local buckling into the outward manner, consequently resulted to higher bearing capacity.

Behaviour of cold-formed steel concrete infilled RHS connections and frames

This paper presents the results of a series of tests carried out on cold-formed steel rectangular hollow and concrete infilled beam to column connections and frames. A stub column was chosen such that overall buckling does not influence the connection behaviour. The beam chosen was a short-span cantilever with a concentrated load applied at the free end. The beam was connected to the columns along the strong and weak axes of columns and these connections were tested to failure. Twelve experiments were conducted on cold-formed steel direct welded tubular beam to column connections and twelve experiments on connections with concrete infilled column subjected to monotonic loading. In all the experiments conducted, the stiffness of the connection, the ductility characteristics and the moment rotation behaviour were studied. The dominant mode of failure in hollow section connections was chord face yielding and not weld failure. Provision of concrete infill increases the stiffness and the ultimate moment carrying capacity substantially, irrespective of the axis of loading of the column. Weld failure and bearing failure due to transverse compression occurred in connections with concrete infilled columns. Six single-bay two storied frames both with and without concrete infill, and columns loaded along the major and minor axes were tested to failure. Concentrated load was applied at the midspan of first floor beam. The change in behaviour of the frame due to provision of infill in the column and in the entire frame was compared with hollow frames. Failure of the weld at the junction of the beam occurred for frames with infilled columns. Design expressions are suggested for the yielding of the column face in hollow sections and bearing failure in infilled columns which closely predicted the experimental failure loads.

Nonlinear Analysis of In-Filled Steel-Concrete Composite Columns

A semianalytical method to predict the behavior of in-filled columns is presented in this paper. Moment-curvature-thrust relationships are generated for column cross sections by an iterative process. Nonlinear equilibrium equations resulting from geometric and material nonlinearities are solved by an incremental-iterative numerical scheme based on the generalized displacement control method. Square, rectangular, and circular cross sections of compact steel tubes filled with concrete are considered in the analysis. The columns are pin-ended and subjected to uniaxial or biaxial loading. The accuracy of the proposed analytical method is established by comparing the results with the corresponding experimental values.